This invention relates generally to an improved method and apparatus for the freezing of comestibles using I.Q.F. (individually quick-frozen) techniques in which the articles in a "fluidized" bed are frozen in an individually separate state rather than in a coherent state. More particularly, such improvements relate to the manner of conditioning the food articles in a fluidized state before being subjected to deep bed mass fluidization in a fluidized state.
A dual conveyor I.Q.F. system for deep freezing of food articles is disclosed by U.S. Pat. No. 3,982,404. The food articles to be frozen are deposited on a first conveyor and are subjected to an upward flow of gas at subfreezing temperature for a first period of time to substantially remove all the above-freezing sensible heat from the food articles without removing the latent and sensible heat. The articles are then subjected to another deeper bed deposit and the gases are flowed upwardly therethrough for a longer time period than the first period so as to remove all the remaining latent heat from the articles.
The aforedescribed dual tandem system thus includes an article-conditioning first stage operated together with a deep bed fluidization second stage freezer. While recognizing the advantages of this dual freezer system, the article-conditioning first stage is not without its shortcomings. Different food products to be frozen (e.g., beans vs. strawberries) require different article conditioning measures to be taken to insure that the food articles are individually frozen without sticking upon leaving the deep bed fluidization second stage. Caking of the food articles persists despite subjecting them in the first stage, as in the prior art, to subfreezing temperature for a relatively short period of time.